Thidiazuron, the common name for N-phenyl-N'-1,2,3-thiadiazol-5-ylurea, is a known cotton defoliant and has been registered for such purpose with the Environmental Protection Agency (EPA). Thiocyanates, in general, have found several agricultural applications such as herbicides, crop desiccants, and defoliants, adjuvants and the like. For example, the cotton defoliant activity of ammonium and alkali metal thiocyantes, is shown in U.S. Pat. No. 2,368,601, issued Jan. 30, 1945 to Robt. E. Torley and assigned to American Cyanamid Company.
In some cases, active agricultural chemicals have been shown to be more effective in combination than when applied individually. The result is often termed "potentiation" or "synergism" since the combination demonstrates a potency or activity level exceeding that which it would be expected to have, based on a knowledge of the individual potencies of the components.
The present invention resides in the discovery that the cotton defoliating activity of thidiazuron is markedly enhanced when used in combination with certain thiocyanates, particularly ammonium thiocyante.